1. Field of the Invention
The present invention relates to a fuel cell including a plurality of unit cells, formed by sandwiching an elongated electrolyte membrane/electrode web member by gas diffusion current collector members. A plurality of anodes and cathodes are provided on both surfaces of the electrolyte membrane/electrode web member.
2. Description of the Related Art
For example, a polymer electrolyte fuel cell employs a membrane electrode assembly (MEA) which includes an anode, a cathode, and an electrolyte membrane interposed between the anode and the cathode. The electrolyte membrane is a solid polymer ion exchange membrane. The membrane electrode assembly and separators sandwiching the membrane electrode assembly make up a unit of a power generation cell for generating electricity. Normally, a predetermined number of the power generation cells are stacked together to form a fuel cell stack.
In the fuel cell, a fuel gas such as a gas chiefly containing hydrogen (hereinafter also referred to as the “hydrogen-containing gas”) is supplied to the anode. A gas chiefly containing oxygen or the air (hereinafter also referred to as the “oxygen-containing gas”) is supplied to the cathode. The catalyst of the anode induces a chemical reaction of the fuel gas to split the hydrogen molecule into hydrogen ions and electrons. The hydrogen ions move toward the cathode through the electrolyte membrane, and the electrons flow through an external circuit to the cathode, creating DC electrical energy.
In particular, in the case where the fuel cells are stacked together to form a fuel cell stack used in a vehicle application, it is desirable to reduce the overall size (height) of the stack for efficiently utilize the limited space in the vehicle.
In this regard, for example, a fuel cell disclosed in Japanese Laid-Open Patent Application No. 6-60905 is known. As shown in FIG. 9, in the fuel cell, a plurality of unit cells 1a, 1b, 1c, and 1d are stacked together. Each of the unit cells 1a to 1d has an air electrode 3, a fuel electrode 4, and an electrolyte 2 interposed between the air electrode 3 and the fuel electrode 4. An air electrode chamber 5 is provided at the air electrode 3, and a fuel electrode chamber 6 is provided at the fuel electrode 4.
The unit cell 1a and the unit cell 1b use the fuel electrode chamber 6 in common. The unit cell 1b and the unit cell 1c use the air electrode chamber 5 in common. Further, the unit cell 1c and the unit cell 1d use the fuel electrode chamber 6 in common.
The air electrode 3 of the unit cell 1a and the fuel electrode 4 of the unit cell 1b are connected by a current collector connector 7a, and the air electrode 3 of the unit cell 1b and the fuel electrode 4 of the unit cell 1c are connected by a current collector connector 7b. Further, the air electrode 3 of the unit cell 1c and the fuel electrode 4 of the unit cell 1d are connected by a current collector connector 7c. In this manner, the unit cells 1a to 1d are connected in series through the current collector connectors 7a to 7c. 
In the fuel cell, each of the unit cells 1a to 1d comprises a unit of the air electrode 3, the fuel electrode 4, and the electrolyte 2. The unit cells 1a to 1d are arranged in a predetermined direction, and stacked together. In order to connect the unit cells 1a to 1d together in series, operation for attaching the current collector connectors 7a to 7c is required. Consequently, the assembling operation of the fuel cell stack is significantly complicated, and time consuming. Thus, productivity for the fuel cell stack is low.
Further, since the unit cells 1a to 1d are connected in series through the current collector connectors 7a to 7c as separate components, the electrical resistance is large, and the number of components of the fuel cell stack is considerably large.